The clock showed 73. The board displayed 14. Stuart Armstrong’s afternoon was over, replaced by Leigh Griffiths.
As he walked off the Celtic Park pitch he took the acclaim of the Celtic fans, his goal the difference as the league leaders led Rangers. After a tepid start to the match, with Rangers taking the game to the heavy favourites, Celtic needed inspiration, and it was provided, not for the first time, by Armstrong.
With Brown stepping up alongside Armstrong, Celtic took control of the second half. But as Rodgers lamented at full-time, the calf injury which prompted the removal of the former Dundee United man saw the home side lose their fluency.
It should be of no major surprise that when Rangers did peg Celtic back, Armstrong was on the sidelines. This is a player who has grown, mentally, physically and technically, under Brendan Rodgers. For someone who may have feared for his future in the summer, Armstrong is now a must-start.
Much is made of Brown’s renaissance under Rodgers, but it is Armstrong who has developed into the midfield fulcrum. The next step is the national team.
Gordon Strachan, watching on from the Sky Sports studio at Celtic Park, names his Scotland team for the upcoming double header against Canada and Slovenia tomorrow. And it would be a huge surprise if the 24-year-old is not named in the squad.
The national team manager told Sky that he has been the “most impressive” Scottish player in the last few months.
“He’s now playing in a position that we all thought was his best position,” Strachan said. “The two most impressive midfielders over the last three or four months, Stuart and Tom Cairney at Fulham.
“They play in similar sort of positions so it is ironic for us that two of our best players at this moment are two midfield players that play in the exact same position.
“But you get as many good players in your squad as you can.
“I think he can run people to the ground, where he actually forces other midfield players to say ‘I can’t go with you any more, I can’t run with you’. His strength and fitness is excellent right now.”
This is man for the big occasion. Even if all those around him are losing their head, he is capable of keeping his. Playing with a zen-like mindset.
Twice in the first half he had to avoid desperate lunges from Rangers players. Kenny Miller did his best Bruce Lee impression early on when he went flying in at Armstrong; any contact and the Celtic midfielder would have been lucky to use his legs again. Thankfully Miller was nowhere near him.
Later on Danny Wilson overran the ball before going in late on Armstrong. Both times he got up and got on with the game. While others would have lost their cool and went looking for retribution, all Armstrong was interested in playing football and driving his team forward.
With Celtic struggling to get a foothold in the first half, their passing game not quite clicking, Armstrong battled and fought. Qualities that are required in the cauldron of a derby, especially one involving the Old Firm.
He went closest for Celtic, hitting the post with a free-kick, before opening the scoring with a fizzing left-footed effort. He had engineered enough space on the edge of the box to get a shot away with his weaker foot. Wes Foderingham, who had his weight on his right, couldn’t get down quick enough to his left to stop it.
It was Armstrong’s second goal in four Old Firm games. He came off the bench in the first encounter to score and in the Ibrox fixture he really should have scored but had to settle with an assist in a dominant second half performance.
However, it was the Betfred Cup semi-final which is most memorable. Because it proved the turning point in his Celtic career.
With Celtic struggling to find a way through a resolute Rangers rearguard, Armstrong was summoned from the bench with 27 minutes left, replacing the ponderous Nir Bitton. He provided everything the Israeli midfielder didn’t. Grit, desire, power, verticality.
Armstrong helped turn a game, which was heading for extra-time, into a big win as Celtic moved a step closer to their first piece of silverware under their new manager. From that point onwards Armstrong won the trust of Rodgers.
He was exceptional in a midweek win over Ross County when Rodgers made sweeping changes. He showed that you do not have to be a bawler to lead. He led by example. Setting the tempo in terms of pressing as well as showing the positivity in possession Rodgers desires.
With the help of Brown, Armstrong dominated the midfield battle in the second half. Running, battling and displaying an abundance of class. Foderingham denied him twice. A zipping effort from inside the box and a curling shot from outside. If either went in, Celtic would have swept home.
Instead, he had to exit with a calf injury and Celtic became disjointed.
If there were any doubts about the importance, and quality, of Stuart Armstrong, those were answered at Celtic Park. His next task is to leave his mark on the Scotland national team. But will Gordon Strachan allow him to do so?